As a semiconductor light emitting device, such as an LED (Light Emitting Diode), there is a structure in which a crystalline layer formed on, for example, a sapphire substrate is joined to a conductive substrate, then the sapphire substrate is removed. In the structure, in order to enhance light extraction efficiency, the surface of the crystal layer exposed by removing the sapphire substrate is subjected to unevenness processing. Moreover, there is also a structure in which no electrode is formed on the surface of the crystal layer to be a light extraction plane and a p-side electrode and an n-side electrode are formed on a crystal plane opposite to the surface from which the sapphire substrate is removed. In such a light emitting device, it is required to further improve the light extraction efficiency by enhancing the heat dissipation property.